Method for expanding and applying a rolling bellows to a connecting part of an air spring and device for carrying out such a method

Abstract

Method for expanding and applying a rolling bellows (1) to a connecting part (2) of an air spring, characterized by - inflating an inflatable bellows (9) of an inflation device (8) with an inflation bellows pressure (pb), so that a rolling bellows (1) surrounding the inflatable bellows (9) at least in part is expanded in an end section (4) and pressed against an externally positioned retaining ring (11), - initiating a chamber pressure (p k ) into a pressure chamber (14), within which the inflation device (8) and the rolling bellows (1) are located, and simultaneously increasing the inflation bellows pressure (p b ), so that it is always greater than the chamber pressure (p k ) is, - release the inflation pressure (p b ), so that a contact pressure from the inflatable bellows (9) against the rolling bellows (1) decreases and the chamber pressure (p k ) presses the bellows (1) against the retaining ring (11), - subsequent movement of the connecting part (2) so that a clamping base (3) of the connecting part (2) is positioned within the widened end section (4) of the rolling bellows (1), - and subsequent release of the chamber pressure (p k ), so that the widened end section (4) of the rolling bellows (1) contracts elastically and comes to bear against the clamping base (3) of the connecting part (2), and device for carrying out such a method.

Description

[0001] The invention relates to a method for expanding and applying a rolling bellows to a connecting part of an air spring according to the preamble of the method claim and a device for carrying out such a method according to the device claim.

[0002] Air springs or air struts, which are clamped between the chassis and the body of a motor vehicle and feature a rolling bellows, which in turn is secured between a cover and a rolling piston, are known in a wide variety of designs. During operation, the air spring is subjected to internal overpressure, and the rolling bellows rolls during spring movements, forming a rolling fold on the outer surface of the concentric rolling piston. To limit expansion, the rolling bellows is enclosed by a sleeve-shaped outer guide.

[0003] Clamping rings are standard for fastening the rolling bellows to the cover and rolling piston at the ends. However, the rolling bellows is first expanded to the diameter of the connecting part while still unvulcanized and then vulcanized to this diameter, so that the fully vulcanized rolling bellows can be more or less easily placed over the clamping base of the connecting part. The end section of the rolling bellows is then pressed against the clamping base of the respective connecting part (cover or rolling piston) using the clamping ring. This creates a pressure-tight connection between the rolling bellows and the connecting part. The radial pressing of the clamping ring represents an additional assembly step. However, clamping using clamping rings has disadvantages. The roundness and flatness of the clamping rings are impaired after the pressing process. Excessive clamping can damage the reinforcements of the rolling bellows.After clamping, the clamping tension decreases by the amount of elastic springback of the clamping components (clamping ring and clamping base). A clamped assembly consisting of a clamping ring and clamping base also loses preload over time due to the creep behavior of the elastomer material of the rolling bellows. Retightening is not possible during operation of the air spring systems. This creates the risk of the rolling bellows slipping out of the clamped assembly.

[0004] For example, in the method according to DE 41 42 725 A1 for tightly fastening a rolling bellows made of an elastomer material to a connecting part of the air spring, an open end of the rolling bellows is pushed onto the connecting part. A metallic clamping ring is then pushed over the rolling bellows and positioned at its end area. The diameter of the clamping ring is reduced by radial compression, so that the end section of the rolling bellows is clamped pressure-tight to the connecting part. The connecting part comprises a clamping base with circumferential projections onto which the open end section of the rolling bellows is pushed. The clamping ring is then pushed onto the end section of the rolling bellows, the diameter of which is reduced by means of clamping segments.

[0005] Before such a clamping process, it is advantageous if the rolling bellows has been positioned so that it cannot slip. However, the end section diameter of the rolling bellows is subject to certain tolerances, meaning that it can move relative to the clamping base. This must be taken into account during the clamping process and is disadvantageous. This sliding on usually requires manual positioning, since the bellows' unstable shape causes the diameter to collapse and thus has a clear inner diameter that is usually too small for direct mechanical sliding on. Usually only manual intervention, sometimes with slight mechanical, elastic expansion, allows the soft bellows end to be pushed onto the dimensionally stable clamping base. However, this also has the crucial disadvantage that the clamping ring then has to be correspondingly larger in order to fit over the bellows, which is actually too large.During the clamping process, the clamping ring must then undergo a correspondingly larger diameter change (clamp down), which is highly detrimental to the achievable clamping performance (clamping strength and tightness). To facilitate handling of the pre-assembled unit consisting of clamping base and bellows in the clamping machine, it would be advantageous if the bellows were connected to the clamping base with a precise, non-slip fit. The bellows can only be clamped successfully once it has been properly pushed onto the clamping base.

[0006] The spring properties of a motor vehicle air spring depend, among other things, on the working volume of the air spring. For example, air spring covers with a wide variety of dimensions are required. However, such volume-encompassing covers also differ in their clamping base diameters for the rolling bellows. This means that each air spring cover requires a specific rolling bellows with an end section diameter matched to the clamping base. This means that a specially matched bellows geometry is required for each clamping base diameter so that the bellows is securely pushed over the clamping base during the clamping process. However, the clamping base diameter is very application-specific and therefore difficult to standardize. This then runs counter to the standardization of rolling bellows shapes and requires a separate bellows type and individual tool molds for vulcanization for each clamping base diameter, which in turn results in high costs.There is therefore a desire to use a rolling bellows with a predefined geometry for connecting parts with a wide variety of clamping base diameters, in accordance with the modular principle.

[0007] It is the object of the invention to provide a method for expanding and applying a rolling bellows with an end section diameter for connecting parts with a larger clamping base diameter, and to provide a device which makes it possible to apply a rolling bellows with an end section diameter to connecting parts with a larger clamping base diameter.

[0008] The problem is solved by the features of the independent method claim and the features of the independent device claim. Preferred embodiments are set out in the respective subclaims.

[0009] The invention is explained in more detail with reference to the following description of the figures. Fig. 1 an exemplary device for expanding and applying an air spring bellows to a connecting part of the air spring, Fig. 2 shows a first method step of an exemplary method for expanding and applying an air spring bellows to a connecting part of the air spring, Fig. 3 a second method step of the exemplary method, Fig. 4 a third process step of the exemplary process, Fig. 5 a fourth step of the exemplary method, Fig. 6 a fifth method step of the exemplary method, and Fig. 7 the rolling bellows attached to the connecting part of the air spring.

[0010] With the Fig. 1, an exemplary device for expanding and applying an air spring bellows to a connecting part of an air spring will first be explained, by means of which the exemplary method for expanding and applying an air spring bellows to a connecting part of the air spring is carried out.

[0011] An essential component of the device is a pressure chamber 14, which comprises a first (upper) chamber part 15 and a second (lower) chamber part 16. Pressure chamber 14 is sealed against the atmospheric environment and configured such that a controllable overpressure or internal pressure of 1 to 8 bar can be applied. This is achieved via a first air connection 20, which is provided, for example, on the first chamber part 15. Preferably, a second air connection 21 is provided on the second chamber part 16, whereby different pressures can be introduced into pressure chamber 14. Pressure chamber 14 is also configured such that components located therein can be moved axially.Furthermore, various control and measuring devices not shown, such as pressure gauges, linear guides, adjusting screws, slides, movement buttons, viewing windows, cameras and others, are provided to detect and adjust the pressure state in the various components as well as their position within the pressure chamber 14.

[0012] The expansion and application of the rolling bellows will take place within pressure chamber 14. The first and second chamber parts 15 and 16 are pot-shaped. They are aligned with their open edges towards each other. A retaining ring 11 lies sealingly on the inside of the area of the chamber parts 14 and 15 that face each other. A seal 13 between the retaining ring 11 and the two chamber parts 14 and 15 is achieved by means of circumferential sealing means arranged between the retaining ring 11 and the inner wall of the respective chamber part 15, 16. The retaining ring 11 has a C-shaped cross-section and two inward-facing retaining lugs. These retaining lugs protrude radially from the retaining ring with a length of approximately 5 to 30 mm and, due to their C-shape, are directed towards each other.

[0013] Furthermore, an inflation device 8 is provided, which comprises an inflatable bellows 9, as well as a first upper inflatable bellows part 17 and a second lower inflatable bellows part 18. Both inflatable bellows parts 17 and 18 are cylindrical and connected to one another by means of a screw connection 19. The screw connection 19 allows the axial distance between the inflatable bellows parts 17 and 18 to be adjusted. A cylindrical inflatable bellows 9, which is shown in the unpressurized state, is attached to the outside of the inflatable bellows parts 17 and 18. Thus, an upper end of the inflatable bellows 9 is attached to the first inflatable bellows part 17, and a lower end of the inflatable bellows 9 is attached to the second inflatable bellows part 18 by means of corresponding clamping rings. Furthermore, the second inflatable bellows part 18 comprises an air connection 10 so that a compressed air source can be connected to the inflation device 8 by means of a hose line.For this purpose, air connection 10 is designed as an axially continuous and stepped bore, which leads to the axial distance between the two inflatable bellows parts 17 and 18, whereby compressed air can be directed into inflatable bellows 9. Preferably, an inflatable bellows pressure of 1 to 8 bar is adjustable. Furthermore, the second inflatable bellows part 18 is designed with an elongated hollow cylindrical section, which lies sealingly in an opening of the second chamber part 16 of pressure chamber 15. In addition, inflation device 8 can be moved in a controlled manner in the axial direction by means of a linear guide (not shown). This allows the axial position of inflatable bellows 9 within pressure chamber 14 to be adjusted.

[0014] A rolling bellows 1 is positioned on the outside of the inflation device 9. The rolling bellows 1 is an elastomeric product provided with reinforcements and is an essential component of a vehicle air spring. The rolling bellows 1 comprises an end section 4, which is designed to be attached to a clamping base 3 of a connecting part 2 of the air spring. This end section 4 needs to be expanded. Due to the elasticity of the rolling bellows material, this end section can be expanded, but internal restoring forces then act, which reverse the expansion. Furthermore, expansion is not so easy due to the embedded reinforcements. Therefore, end section 4 of the rolling bellows 1 is positioned such that it lies in the area of the inflation bellows 9, so that it can later be expanded by the latter. A holding device (not shown) is provided for the rolling bellows 9, by means of which the latter can be moved in a controlled manner in the axial direction.In the illustration, the rolling bellows 1 has a cylindrical shape, but other configurations of the rolling bellows 1 are also possible, for example, a conical shape. Furthermore, the rolling bellows 1 extends along the wooden cylindrical section of the second inflatable bellows part 18. Furthermore, the rolling bellows 1 is presented in a fully vulcanized state. Therefore, it is not an unvulcanized rolling bellows blank.

[0015] For example, an air spring cover is used as the connecting part 2, which is also designed to be voluminous. However, the rolling piston of an air spring can also be used as the connecting part. Connecting part 2 has a clamping base 3, against which the end section 4 of the rolling bellows 1 is to be placed and clamped using a clamping ring. As can be seen from the figure, a clamping base diameter 5 of connecting part 2 is larger than an end section diameter 6 of the rolling bellows 1. A holding device (not shown) is provided for connecting part 2, by means of which the connecting part 2 can be moved in a controlled manner in the axial direction.

[0016] Starting with the Fig. 2 now describes the exemplary procedure for expanding and applying.

[0017] Connecting part 2, rolling bellows 1 and inflation device 8 are inserted into the pressureless pressure chamber 14 and the pressure chamber 14 is closed. Inflation device 9 is pressurized to pressure p bof 3 bar, causing the inflatable bellows 9 to inflate and the rolling bellows 1 to expand in the corresponding area, until the rolling bellows 1 is pressed against the retaining ring 11 in the expanded area. The C-shaped retaining ring 11, with its lugs, forms an inwardly open cavity into which the outer side of the pressed-on rolling bellows 1, with its rubberized surface, presses airtight, thus sealing the cavity. The retaining ring 11 also has an inner diameter that is larger than the clamping base diameter of the connecting part 2.

[0018] For example, retaining ring 11 is designed to be interchangeable. This means that retaining ring 11 can be replaced with other retaining rings with different geometries. This increases the variability depending on the required bellows diameter, clamp base diameter and force requirement. Retaining rings with different inner diameters are used to enable the use of different clamp base and bellows geometries. The axial distance between the retaining lugs can be changed to control the holding force while otherwise maintaining the same chamber pressures. The contour of the retaining lugs or their sharpness can also be adjusted to implement different penetration behavior of the bellows rubber into the retaining lugs. The radial distance between the retaining lugs and the profile base can also be adjusted to implement different curvatures of the inflatable bellows 9 when pressed against the retaining ring cavity.

[0019] In the next step, according to the Fig. 3 the pressure chamber 14 with a pressure p k to 5 bar, for example. The pressure p b in the inflation device 8 and set to, for example, 8 bar. As a result, the pressure in the inflation device 8 is always greater than in the pressure chamber 14, which ensures that the rolling bellows 1 is always pressed sealingly against the retaining ring 11 in the expanded area. Depending on the nature and diameter of the bellows to be expanded, different elastic restoring forces arise in the bellows, while the bellows should remain pressed sealingly against the retaining ring 11. Particularly with robust bellows and bellows without external guidance, or bellows with a large expansion and a high standardization of the vulcanized bellows diameter, considerably high holding forces on the retaining ring 11 may be required. In order to apply these holding forces, the device makes it possible to adjust the chamber pressure p k to e.g. 20 bar in order to generate any desired holding force.

[0020] The position of retaining ring 11 and its sealing closure by the pressed-on bellows 1 essentially divides the cavity of pressure chamber 14 into an upper and lower section. This makes it possible, for example, to connect these sections pneumatically. This has the advantage of enabling a simple structure but also of controlling the chamber pressure p k to be set differently in both areas. This can be advantageous for the subsequent process step.

[0021] In the critical process step according to the Fig. 4, the inflation device 8 is vented. In doing so, the holding function of the inflatable bellows 9 must be transferred to the chamber pressure so that the sealing of the cavity on the retaining ring 11 is not interrupted and the rolling bellows 1 with its expanded area continues to be held on the retaining ring 11. By venting the inflation device 8, the contract pressure between the inflatable bellows 9 and the rolling bellows 1 is reduced. The chamber pressure penetrates between the inflatable bellows 9 and the rolling bellows 1. Accordingly, the chamber pressure now presses on the rolling bellows 1 and no longer on the inflatable bellows 9. The contact pressure presses the rolling bellows 1 against the retaining ring 11 so that sufficiently large expanding forces hold the rolling bellows 1 in its expanded shape and counteract the elastic restoring forces of the rolling bellows 1. The connection between the cavity of the retaining ring 11 and the environment remains sealed. The inflation device 8 is vented until the holding function of the inflation bellows 9 is no longer required.From now on, the pressure in the inflatable bellows 9 can be completely reduced so that it shrinks and loses contact with the rolling bellows 1.

[0022] If two different pressures are set in pressure chamber 14 during this critical transition, it is easily possible to vary the contact pressure between inflatable bellows 9 and rolling bellows 1 in the axial direction by utilizing the restoring forces of rolling bellows 1. The result is that in the area of the inflatable bellows 9 facing the chamber area with a lower internal pressure, high holding forces are still present because the pressure difference to the inflatable bellows pressure is greater. In contrast, the contact pressure in the area of the inflatable bellows 9 facing the chamber area with a higher chamber pressure decreases because the pressure difference to the pressure in the inflatable bellows 9 is smaller. As a result, the access of the pressure on the side with the higher chamber pressure is opened earlier and thus promotes the assumption of the holding function by the chamber pressure in this area.This increases the capability of the device as a whole because the holding function with the chamber area of lower pressure occurs simultaneously with the penetration function / assumption of the holding function by the chamber pressure.

[0023] In general, the compressed air supply is an important aspect. Filling the bellows 9 and pressure chamber 14 consumes a relatively large amount of compressed air. Therefore, it is proposed not to use compressed air from a compressed air network with shut-off valves and regulators, but rather to provide the compressed air changes through large-volume working cylinders or bellows, which can generate the chamber pressures in one go. This prevents the air used to generate pressure from being extracted from the environment, compressed, and released back into the environment (which is a wasteful use of energy in compressed air generation), but rather to be reused repeatedly in a closed process without releasing any significant amount of air into the environment.This type of generation is combined with a connection of the mechanical drives of these pressure generators of at least two devices in such a way that the conservative energy released when one device expands is used to conservatively compress the air in the other device. This reduces the energy consumption, for example when two devices are coupled, by about half. In another embodiment, pressure chamber 14 is lined with inserts to reduce the dead volume, i.e. the volume around connecting part 2, rolling bellows 1 and inflation device 8 which is not required for the movement of the components as a package. This means that overall less compressed air mass is required to implement a specific required pressure change in pressure chamber 14 or the inflation bellows 9.

[0024] As already explained, during the venting of the inflatable bellows 9, the holding function must be shifted from the contact pressure between the inflatable bellows 9 and the rolling bellows 1 to the application of the chamber pressure. If this shift is insufficient or too slow, there is a risk that the rolling bellows 1 will lift off the retaining ring 11 and the chamber pressure will escape. In contrast, an intermediate body (not shown) can be inserted between the inflatable bellows 9 and the rolling bellows 1 before the inflatable bellows 9 inflates. This intermediate body is characterized by the properties of being expandable in the circumferential direction, whereby the required deformation forces are low. It can transmit the contact pressure between the inflatable bellows 9 and the rolling bellows 1 at least pointwise in the radial direction. The intermediate body is permeable to air. An example of such an intermediate body could be a ring made of a net structure with thick yarns and fine meshes. If the mesh size and the yarn thickness, for example,are on the order of 1 mm, then neither the inflatable bellows 9 nor the rolling bellows 1 are capable of elastically following each individual unevenness of such a mesh structure under contact pressure to such an extent that the unevenness is filled in a sealed manner. Nevertheless, the contact pressure is transmitted sufficiently consistently across the yarn thickness without creating a sealed seal. The extensibility, contact pressure transmission, and air permeability are all present. Another example is an intermediate body consisting of several layers of a mesh structure as described above, which enhances the desired ability for the chamber pressure to penetrate.

[0025] Another example is a ring made of a tangled, elastic material, which can be produced from elastic materials, for example, by 3D printing and has a porous structure. Another example is a chain held by an elastic (rubber) ring and made of many rod-shaped elements with a height approximately 1.5 to 2 times the height of the holding ring 11 and a width and depth of approximately 1 mm. A ring of this type can elastically adapt radially to the movement of the bellows, transmit the contact pressures via its thickness and admit the chamber pressure via the spaces between the elements. Another example is a ring made of sub-elements that interlock in the circumferential direction like a dovetail and are also held movable relative to one another like a chain via an elastic ring.Another design for such chain-like rings is that, instead of a connected ring, the elements rest on long fingers that can move inward and outward around their base point. The base points themselves are movably arranged on a ring below the region of the retaining ring, for example, at the base point of the bellows. The advantage of such an intermediate ring is that it combines the necessary functions of being able to transmit contact pressures between the bellows and, on the other hand, not sealing this contact, thus ensuring that the chamber pressure does not penetrate when the inflatable bellows is vented.

[0026] According to the procedural step after the Fig. 5, the inflation device 8 is now removed from the area to be clamped by moving it axially downwards. Subsequently, the connecting device 2 is moved axially downwards and brought into position in the area to be clamped. This means that the clamping base 3 is pushed into the expanded end area of the rolling bellows 1. The chamber pressure p k is maintained so that bellows 1 is kept open and connecting part 2 can be inserted.

[0027] The following is in accordance with the Fig. 6 the pressure chamber 14 is vented so that the expanded area of the rolling bellows shrinks and its end area rests on the clamping base 3 of connecting part 2.

[0028] Finally, according to the Fig. 7 Connecting part 2 with the attached rolling bellows 1 can be removed from the opened pressure chamber. In a later assembly step, the rolling bellows 1 attached to the connecting part 2 can then be pressure-tightly connected using a clamping ring. List of reference symbols 1 rolling bellows 2 connecting part 3 clamping base 4 Final section 5 clamp base diameter 6 unexpanded end section diameter 7 flared end section diameter 8 inflation device 9 Bellows 10 Air connection for inflation device 11 Retaining ring 12 retaining lugs 13 Sealing 14 pressure chamber 15 first chamber part 16 second chamber part 17 first bellows part 18 second bellows part 19 Screw connection 20 first air connection pressure chamber 21 second air connection pressure chamber p b Bellows pressure p k Chamber pressure

Claims

[1] Method for expanding and applying a rolling bellows (1) to a connecting part (2) of an air spring, characterized by - inflating a bellows (9) of an inflation device (8) with a bellows pressure (p b ), so that a rolling bellows (1) surrounding the inflatable bellows (9) at least in part is widened in an end section (4) and pressed against an externally positioned retaining ring (11), - initiating a chamber pressure (p k ) into a pressure chamber (14), within which the inflation device (8) and the rolling bellows (1) are located, and simultaneously increasing the inflation bellows pressure (p b ), so that it is always greater than the chamber pressure (p k ) is, - release the inflation pressure (p b ), so that a contact pressure from the inflatable bellows (9) against the rolling bellows (1) decreases and the chamber pressure (p k ) presses the bellows (1) against the retaining ring (11), - subsequent movement of the connecting part (2) so that a clamping base (3) of the connecting part (2) is positioned within the widened end section (4) of the rolling bellows (1), - and subsequent release of the chamber pressure (p k ), so that the widened end section (4) of the rolling bellows (1) contracts elastically and comes to rest against the clamping base (3) of the connecting part (2). [2] Method according to claim 1, characterized by that when, after inflation of the bellows (9), the rolling bellows (1) is pressed against the retaining ring (11), the pressure chamber (14) is divided into a first and a second pressure region due to the retaining ring (11) sealingly abutting within the pressure chamber (14), and a different chamber pressure (p k ) is introduced into the two pressure areas. [3] Method according to claim 1 or 2, characterized bythat before the connecting part (2) is moved and the inflation device (8) is vented, it is moved out of the widened end section (4). [4] Method according to one of claims 1 or 3, characterized by that an intermediate body is inserted between the inflatable bellows (9) and the rolling bellows (1), which is elastic and gas-permeable. [5] Device for expanding and applying a rolling bellows (1) to a connecting part (2) of an air spring, characterized by a pressure chamber (14), wherein an inflatable bellows device (8) is arranged at least partially within the pressure chamber (14) and this comprises an inflatable bellows (9), wherein the rolling bellows (1) is arranged at least partially around the inflatable bellows (9), wherein the connecting part (2) is arranged within the pressure chamber (14) and the rolling bellows (1) has an end section diameter (6) which is smaller than a clamping base diameter (5) of the connecting part (2). [6] Device according to claim 5, characterized by that the pressure chamber (14) comprises a first and a second chamber part (15; 16). [7] Device according to claim 6, characterized by that an internal retaining ring (11) is sealingly arranged in a contact area of the first and second chamber parts (15; 16), so that the pressure chamber (14) is closed off from the atmosphere. [8] Device according to one of claims 5 to 7, characterized by that the pressure chamber (14) comprises at least one air connection (20, 21). [9] Device according to one of claims 5 to 8, characterized by that an elastically deformable and gas-permeable intermediate body is arranged between the inflatable bellows (9) and the rolling bellows (1). [10] Device according to one of claims 5 to 9, characterized by that the connecting part (2) can be moved axially within the pressure chamber (14) by means of a holding device.

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